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HTML 

              
                <div class="mm-menu">
  <a href="javascript:;" class="mm-item"><span class="fontawesome-home"></span></a>
  <a href="javascript:;" class="mm-item"><span class="fontawesome-comment"></span></a>
  <a href="javascript:;" class="mm-item"><span class="fontawesome-th"></span></a>
  <a href="javascript:;" class="mm-item"><span class="fontawesome-camera"></span></a>
  <a href="javascript:;" class="mm-item"><span class="fontawesome-cog"></span></a>
</div><!--/mm-menu-->
!

CSS 

              
                @import "compass/css3";

@import url(http://weloveiconfonts.com/api/?family=fontawesome);

$mm-n: 5;
$mm-item-size: 4.5em;
$mm-menu-width: $mm-item-size * $mm-n;

$white: hsl(215, 18%, 97%);
$gray: hsl(215, 8%, 85%);
$slate: hsl(160, 6%, 78%);
$icon: hsl(0,0%,79%);

html,body { height:100%; position:relative }
body {
  margin: 0;
  background: radial-gradient(circle at 40% 0%,#eee 10%,#999);
}

.mm-menu {
  font-size: 1rem;
  position: relative;
  width: $mm-menu-width; height: $mm-item-size;
  border-radius: 0.15em;
  background: $slate;
  box-shadow:
    0 -1px 0.3em rgba(#002,.2) inset,
    0 -1px 1px rgba(#002,.03) inset,
    2px 2px 3px rgba(#002,.2);
// Screen Centering:
  margin: ($mm-item-size / -2) auto 0;
  top: 50%;
}

.mm-item > [class*="fontawesome-"]::before {
  display: block;
  font-family: 'FontAwesome';
  font-size: 2em;
  text-align: center; line-height: $mm-item-size / 2;
  color: $icon;
  text-shadow:
    0 -0.03em rgba(#000,.21),
    0 0.03em 0.06em rgba(#fff,.5);
}

.mm-item {
  @include box-sizing(border-box);
  display: block; position: relative;
  top: -0.25em; float: left;
  width: $mm-item-size; height: $mm-item-size;
  text-decoration: none;
  border-radius: 0.15em;
  transition: 250ms;
  background: linear-gradient($white,$gray) 0 50%;
  background-size: 100% 200%;
}

.mm-item:hover {
  top: -0.35em;
  background-position: 0 0%;
}

.mm-item:focus,
.mm-item:active {
  outline: none;
  top: -0.15em;
  background-position: 0 100%;
}

.mm-item,
.mm-item:first-of-type:focus,
.mm-item:first-of-type:active,
.mm-item:hover:focus + .mm-item,
.mm-item:hover:active + .mm-item {
  box-shadow:
    1px 1px 0 0 rgba(#fff,.15) inset,
    0 0 0 0 rgba(#000,0) inset,
    0.2em 0.2em 0.3em -0.07em rgba(#fff,.6) inset,
    -0.2em -0.3em 0.3em -0.07em rgba(#000,.08) inset;
} 

.mm-item:hover + .mm-item,
.mm-item:focus,
.mm-item:active {
  box-shadow:
    0 0.3em 0.3em -0.2em rgba(#fff,.6) inset,
    1px 0 0 0 rgba(#000,.02) inset,
    0.35em 0 0.3em -0.2em rgba(#002,.07) inset,
    -0.2em -0.3em 0.3em -0.07em rgba(#000,.08) inset;
}

.mm-item:hover + .mm-item:focus {
  box-shadow:
    0 0.3em 0.3em -0.2em rgba(#fff,.6) inset,
    1px 0 0 0 rgba(#000,.01) inset,
    0.45em 0 0.3em -0.2em rgba(#002,.09) inset,
    -0.2em -0.3em 0.3em -0.07em rgba(#000,.08) inset;
}


// ******************************* //
// The following code is simply a technique I just came up with which uses a media query to specifically style certain elements differently when it is in the Codepen preview mode.
// In this case I use it to increase the overall size of the UI Bar, add the hover state effect to the 1st button, and add the pressed effect to the 3rd button.

@media only screen and (height: 300px) {
  .mm-menu { font-size:1.5rem }
  .mm-item:nth-of-type(1) {
    top: -0.35em;
    background-position: 0 0%;
    &::after { top:$mm-item-size + 0.3em }
  }
  .mm-item:nth-of-type(2) {
    box-shadow:
      0 0.2em 0.3em -2px rgba(#fff,.6) inset,
      -1px -1px 0 0 rgba(#000,.03) inset,
      0.3em 0 0.2em -2px rgba(#000,.05) inset,
      -0.2em -0.2em 0.3em -2px rgba(#000,.08) inset;
  }
  .mm-item:nth-of-type(3) {
    top: -0.15em;
    background-position: 0 100%;
    box-shadow:
      0 0.2em 0.3em -2px rgba(#fff,.6) inset,
      -1px -1px 0 0 rgba(#000,.03) inset,
      0.3em 0 0.2em -2px rgba(#000,.05) inset,
      -0.2em -0.2em 0.3em -2px rgba(#000,.08) inset;
    &::after { top:$mm-item-size + 0.1em }
  }
  .mm-item:last-of-type::before { width:43.4% }
}
!

JS 

              
                // JS needed to simulate the "sticky" focus state, aka stay pressed down, in chrome:

$(".mm-item").click(function() {
  $(this).focus();
});
!
999px

Console